Related Experiment Video
Updated: Oct 23, 2025
08:46
Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of PhosphorusI
Published on: November 22, 2016
7.9K
Using JPP to Identify Ni Bidentate Phosphine Complexes In Situ.
Matthew D Hannigan1, Anne J McNeil1,2, Paul M Zimmerman1
1Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States.
Inorganic Chemistry
|August 18, 2021
Summary
Phosphorus-31 NMR coupling constants (JPP) in nickel bidentate phosphine complexes can indicate nickel oxidation states. The JPP values vary predictably with linker length and ligand electronic properties, enabling in situ analysis.
Area of Science:
- Organometallic Chemistry
- Inorganic Chemistry
- Spectroscopy
Background:
- Nickel complexes are highly reactive and sensitive to air/moisture, complicating reaction intermediate identification.
- While 31P NMR is useful for diamagnetic nickel bidentate phosphine complexes, determining nickel oxidation state from chemical shifts alone is difficult.
- The P-P coupling constant (JPP) has been suggested to correlate with oxidation state, but its dependence on structural and electronic factors is not well understood.
Purpose of the Study:
- To investigate the utility of JPP values in determining the oxidation state of nickel in bidentate phosphine complexes.
- To explore how linker length and ligand identity influence JPP values.
- To establish reliable JPP-based correlations for in situ oxidation state determination of nickel.
Main Methods:
- Synthesis and characterization of nickel bidentate phosphine complexes with varying linker lengths (two- and three-carbon).
- In situ 31P NMR spectroscopy to measure JPP values.
- Analysis of the correlation between observed |JPP| values and nickel oxidation states (Ni0 vs. NiII).
Main Results:
- Observed |JPP| values effectively indicate the nickel oxidation state.
- For two-carbon linkers, |JPP| > 40 Hz suggests Ni0, while |JPP| < 30 Hz suggests NiII.
- This trend is reversed for three-carbon linkers.
- Lewis acidity/basicity of nickel and phosphine ligands predictably influence JPP values, with increased P-to-Ni donation leading to more negative JPP.
Conclusions:
- JPP coupling constants in 31P NMR are competent indicators of nickel oxidation states in bidentate phosphine complexes.
- The observed JPP trends are dependent on linker length and ligand electronic properties.
- These findings enable reliable in situ determination of nickel oxidation states and ligand properties during reactions.
Related Concept Videos
01:13¹H NMR: Complex Splitting
1.4K
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied...
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied...
1.4K
02:30Chirality at Nitrogen, Phosphorus, and Sulfur
6.2K
Chirality is most prevalent in carbon-based tetrahedral compounds, but this important facet of molecular symmetry extends to sp3-hybridized nitrogen, phosphorus and sulfur centers, including trivalent molecules with lone pairs. Here, the lone pair behaves as a functional group in addition to the other three substituents to form an analogous tetrahedral center that can be chiral.
A consequence of chirality is the need for enantiomeric resolution. While this is theoretically possible for all...
A consequence of chirality is the need for enantiomeric resolution. While this is theoretically possible for all...
6.2K
01:19Inductively Coupled Plasma–Mass Spectrometry (ICP–MS): Overview
1.1K
In inductively coupled plasma–mass spectrometry (ICP–MS), an inductively coupled plasma (ICP) torch is used as an atomizer and ionizer. Solid samples are dissolved and volatilized before being introduced into the high-temperature argon plasma, while solution samples are nebulized and passed through the high-temperature argon plasma. Plasma dissociates the analytes and ionizes their component atoms to form a mixture of positive ions and molecular species. The positive ions are then...
1.1K